1. Field of the Invention
The present invention relates to a belt receptor for use in a color printer and, more particularly, to an apparatus for isolating disturbances in a belt receptor of a color printer.
2. Description of the Related Art
In color printing, a plurality of images are recorded and developed on a member such as an electroreceptor belt. Each image corresponds to one of a plurality of colors. For example, red, green and blue images can be recorded and developed on an electroreceptor belt to form three color separations, the three color separations being superimposed to form a single color image.
In a multiple-pass color printer, each of the red, green and blue color separations is transferred from the electroreceptor belt to a recording medium. The transfer is performed such that the three color separations are positioned in superimposed relationship to one another to form the color image.
In single-pass color printers, the red, green and blue color separations are superimposed on the electroreceptor belt prior to transfer to the recording medium. The color separations are superimposed on the electroreceptor belt by successive imaging stations located adjacent the electroreceptor belt. Each imaging station records an image corresponding to one of the colors. The single color image is developed with toner particles of a color complementary thereto prior to transfer to the recording medium. Various recording mediums can be used in conjunction with these color printers such as a sheet of paper, a transparency, etc.
To achieve a quality image which is not blurred in appearance and which does not contain unwanted artifacts, the color separations must be accurately provided in superimposed relationship while avoiding any motion-induced image degradation. Accordingly, the motion of the electroreceptor belt must be finely controlled, particularly in the span of the electroreceptor belt which encompasses the imaging and developing stations forming the images.
The transfer of an image to a recording medium is performed at a transfer station having a transfer nip. Often, as the recording medium enters the transfer nip, an impulsive and high-frequency force disturbance occurs which is commonly called "thumping". This disturbance impairs the fine control of the motion of the electroreceptor belt which is required to achieve proper tone uniformity and relative registration of the color separations. Because of frequency bandwidth limitations, this disturbance cannot be corrected by known servo mechanism technology. Such servo mechanism technology enables correction only of slowly and smoothly varying force disturbances introduced by other process components such as cleaners, etc.
U.S. Pat. No. 3,656,674 to Morse discloses a web tension isolator for isolating a web within a particular area of a web advancing mechanism from tension forces acting on the web in other regions of the web advancing mechanism. On each side of the isolated portion of the web, a freely rotatable pulley mounted on a pivoted arm interacts with a driver pulley to keep the ratio of the tensions in the web on each side of the pulleys substantially constant. The region of the web between the pairs of pulleys is thus isolated from web tension fluctuations.
U.S. Pat. No. 3,732,402 to Boyer discloses an electromechanical device for a tape winding mechanism wherein vibrations and pulley arrangements are reduced to a maximum extent possible. In the tape winding mechanism, a shock absorber and tensioning device are disposed on each side of a tape reading area to prevent harmful vibration. The shock absorber devices comprise a pair of coil springs connected between a pair of actuating solenoids and a pivot arm. Each pivot arm supports a roller which bears against the tape.
The above references do not disclose belt receptor modules which can achieve the fine control required to obtain proper relative registration of color separations as a recording medium enters the transfer nip.